Double-ended stud-like fasteners consisting of a machine screw thread on one end, a pancake-type flange or head in the middle and a special thread tapping screw at the other end are commonly used in environments where the primary supporting surface is of a plastic-type material with securement therein being a blind application.
Typical applications of this type are those of automotive where plastic components are provided with boss-like protuberances having preformed bores in order to accept the tapping thread end of the stud. The studs are usually first driven into the plastic bosses with a stud driver leaving the machine screw end to be inserted later through clearance holes in sheet metal workpieces. Nuts are then used to clamp the sheet metal against the pancake head of the double-ended stud which puts all the load on the machine screw end of the stud and eliminates any added stress to the plastic during installation.
A typical manner of driving such double-ended studs has been to utilize the upwardly extending threaded shank and transmit torque to the fasteners by means of a chuck grasping the threaded section. Another method utilizes the outer periphery of the flange to drive the fastener. Such applications and tools tend to be significantly greater in diameter than the diameter of the flange and/or the boss which the stud is to be associated with. In many such applications, the bosses are in confined areas and size of the tool is a definite factor in efficiently driving such fasteners.
In addition to the application or driving problems associated with prior art systems, a substantial problem exists in securing the fastener from backing out or rotation tending to remove after the fastener has been installed. For a variety of reasons, the clamping nuts may have to be removed and/or the sheet metal removed from the installation. When torque is applied to the system to remove the nut, it is also applied to the stud tending to loosen or remove the stud itself from the plastic. A number of techniques have been suggested to eliminate this tendency to remove the stud when the nut is removed. Adhesives, special thread forms, locking means beneath the pancake head or a combination of special configurations of boss and pancake head have been suggested. However, the prior art suggestions are either costly, cumbersome or contributory to further deterioration and stressing of the plastic during installation.